1. Field of the Invention
This invention relates to a pneumatic tire having an improved uniformity at a tire-wheel assembled state. More particularly it relates to a pneumatic tire capable of lessening radial runout (hereinafter abbreviated as RRO) and effectively controlling radial force variation (hereinafter abbreviated as RFV) by providing satisfactory uniformity at a tire-wheel assembled state when the tire is mounted on a rim standardized in Japan Automobile Tire Manufacturing Association (JATMA), The Tire and Rim Association, Inc. (TRA) or the like (hereinafter referred to as a "standard rim" such as a two piece divided type rim, 5 degree full drop center rim, 15 degree full drop center rim, wide flat base rim and the like.
2. Description of the Related Art
As to the reduction of RFV in a tire-wheel assembly after a pneumatic tire is mounted on a rim, Japanese Patent laid open No. 3-189201 discloses that a spacer is interposed between a bead portion of the tire and a flange of the rim at a position corresponding to a large value of RRO measured at a shoulder portion of the tire in its circumference. In this case, however, it is required to repeat the operation of assembling the tire on the rim and supplying air into the tire, which considerably obstructs the operability of the rim assembling. Also there is a fear of causing a disorder due to external force applied to the tire-wheel assembly.
On the other hand, it is known that the tire after the vulcanization is mounted onto the rim so as to have a position of maximum peak in a waveform showing the change of RFV measured on the tire itself coincide with a position of minimum peak in a waveform showing a variation of scale deflection separately measured on the outer periphery of the rim. However, such rim assembling is no longer meaningless owing to the improvement of rim working accuracy.
With the advance of studies on ride comfortability against vibrations and noise of automobiles, particularly passenger cars, uniformity at tire-wheel assembled state becomes important.
The term "uniformity at tire-wheel assembled state" does not mean that the tire-wheel assembly is merely a true circle in its shape, but means that the deflection on the periphery of the assembly is equal at any positions under the same load or the reaction force and is uniform during the rotation of the assembly under a certain deflection because RRO among the measures for the evaluation of the uniformity or the scale deflection of the outer periphery on the tire and rim degrades the variation of radial reaction force or RFV when the tire-wheel assembly is rotated under a certain deflection.